DESCRIPTION (adapted from abstract): This is a competing renewal application for a grant funded for the past two years. In a continuing effort to develop an appropriate molecular model to study the cellular defense of heart against ischemic reperfusion injury, genetically engineered animals will be developed and the molecular signaling process will be evaluated. Based on their recent findings that oxygen free radicals function as second messengers in signal transduction leading to phosphorylation and activation of heat shock protein (HSP) 27, the investigators propose to develop transgenic and knockout mice for HSP 27 and a related HSP--alpha, beta- crystallin. To test the importance of redox signaling in myocardial ischemia/ reperfusion, mice genetically engineered to affect two major proteins in redox regulation, thioredoxin and glutaredoxin, will be developed. Since significant amounts of cross-talk exist between heat shock and antioxidant proteins and since redox-sensing proteins can regulate HSP, the investigators will study the underlying mechanisms by examining the regulatory steps in intracellular signaling. Molecular signaling will be correlated with standard measures of myocardial preservation, including ventricular functions, cellular injury and infarction. Apoptosis and DNA fragmentation as well as development of oxidative stress associated with ischemic reperfusion injury will also be studied, as these parameters are closely related to redox systems. Finally, the expression of the three transcription factors AP-1, p53 and NFkB and the two protonocogenes c-jun and c-fos will be examined, because these transcription factors and oncogenes are believed to be the molecular links between ischemia/ reperfusion- induced signal transduction and gene expression leading to the expression of heat shock and antioxidant proteins. The results of these studies will demonstrate the molecular mechanisms of constitutive cellular protection against myocardial ischemia/ reperfusion injury by examining the redox signaling process.